Semiconductor quantum dots based on protein assembly and peptide anchoring, their preparation methods, and their applications in artificial photocatalysis

Abstract

The present application proposes a semiconductor quantum dot based on protein assembly and peptide anchoring, its preparation method and application in the field of artificial photocatalysis, which relates to the field of bionanomaterial technology. The preparation method is as follows: MBP is fused to the N-terminus of the sequence of the cyclic protein SP1, and a double histidine group is introduced by mutation to construct a fusion plasmid, which is transformed into the Escherichia coli BL-21 strain for expression, and a protein mutant solution is obtained after purification; the protein mutant is incubated with CdCl2 and Na2S in sequence to obtain an SP1-CdS quantum dot hybrid; or the protein mutant is first incubated with an ion chelator, and then the above-mentioned CdCl2 and Na2S incubation is repeated to obtain an SP1-CdS quantum dot hybrid assembly. The product is highly designable and modifiable, can be adapted to a variety of electron sacrificial agents to achieve efficient hydrogen production, has high stability and can arrange photosensitizers and photocatalytic centers in an orderly and fixed manner, and has great development prospects and application potential.

Description

Technical Field

[0001] The present application relates to the technical field of bionanomaterials, and in particular to a semiconductor quantum dot based on protein assembly and peptide anchoring, a preparation method thereof, and an application thereof in the field of artificial photocatalysis. Background Art

[0002] The continued use of non-renewable energy sources has led to a severe energy crisis worldwide. The construction of artificial photocatalytic systems to achieve photocatalytic hydrogen production provides inspiration and ideas for solving this pressing problem.

[0003] Common photocatalysts, such as inorganic nanoparticles, are difficult to disperse and suffer from electrostatic aggregation, which leads to a sharp decrease in stability, significantly limiting their application. Furthermore, studies have shown that the 2D arrangement of catalytic centers can provide the system with a larger surface area and easily accessible catalytic sites for faster electron and mass transfer. However, due to the poor solubility of inorganic particles, constructing artificial photocatalytic hydrogen production systems with orderly arranged catalytic centers faces significant challenges.

[0004] Therefore, constructing an artificial photocatalytic system with good stability, high photoelectric performance and orderly arrangement of photocatalytic centers has important practical significance and also shows great development prospects and application potential. Summary of the Invention

[0005] In response to the defects of inorganic photocatalysts in the existing technology, such as difficulty in dispersion and orderly arrangement, and electrostatic precipitation leading to a sharp decrease in their stability, the present application provides semiconductor quantum dots based on protein assembly and peptide anchoring, as well as their preparation method and application in the field of artificial photocatalysis. It can achieve efficient photocatalytic hydrogen production, and at the same time can arrange photosensitizers and catalytic center nanoparticles in a targeted, orderly and compact manner, with the characteristics of high stability and good photoelectric performance.

[0006] In order to solve the above technical problems, the technical solutions adopted in this application are:

[0007] In one aspect, the present application provides a method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring, comprising the following steps:

[0008] S1. Using genetic engineering methods, MBP was fused to the N-terminus of the sequence within the SP1 ring protein cavity, and a double histidine group was introduced by mutation at a suitable site on the protein surface to construct a fusion plasmid. The plasmid DNA was transformed into the Escherichia coli BL-21 strain for expression, and purified using anion exchange columns and dextran gel columns to obtain a protein mutant solution.

[0009] S2, mixing the protein mutant solution with a CdCl2 solution under nitrogen protection and incubating, and then adding a Na2S solution and incubating again to obtain an SP1 protein-CdS quantum dot hybrid;

[0010] Alternatively, the protein mutant solution is first incubated with an ion chelator, and then a CdCl2 solution is added to the system, mixed and incubated under nitrogen protection, and finally a Na2S solution is added and incubated again to obtain an SP1 protein-CdS quantum dot hybrid assembly.

[0011] On the other hand, the present application provides a semiconductor quantum dot based on protein assembly and peptide anchoring, wherein the semiconductor quantum dot is specifically an SP1 protein-CdS quantum dot hybrid or an SP1 protein-CdS quantum dot hybrid assembly, which is prepared using the above-mentioned preparation method.

[0012] On the other hand, the present application provides an application of semiconductor quantum dots based on protein assembly and peptide anchoring in the field of artificial photocatalysis.

[0013] Compared with the prior art, the embodiments of the present application have at least the following advantages or beneficial effects:

[0014] This application describes the in situ biosynthesis of semiconductor quantum dots based on proteome assembly and peptide anchoring. The protein template is highly designable, allows for directional modification, and exhibits high biocompatibility. The building block is the cyclic stabilizing protein 1 (SP1), which incorporates a metal-binding peptide within its natural 4nm cavity, enabling spatially confined anchoring and in situ growth of CdS quantum dot photosensitizers.

[0015] 2. The semiconductor quantum dots prepared in this application are based on protein assembly, which can orderly arrange the catalytic center quantum dots synthesized in situ, enhance their photoelectric separation performance, effectively avoid the random aggregation of inorganic nanoparticles, and thus improve the stability of the catalytic system.

[0016] 3. Experiments have shown that depositing noble metal nanoparticles on the surface of semiconductor quantum dots to form a heterojunction structure can effectively improve the performance of photocatalytic hydrogen production.

[0017] In summary, the semiconductor quantum dots based on protein assembly and peptide anchoring in this application are highly designable and modifiable, can be adapted to a variety of electron sacrificial agents to achieve efficient hydrogen production, are highly stable and can arrange photosensitizers and photocatalytic centers in an orderly and targeted manner, showing great development prospects and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a transmission electron microscope image of CdS formed from the solution in Comparative Example 1 of the present application;

[0020] Figure 2 is a transmission electron micrograph of the CdS@MBP-SP1-2His hybrid in Example 1 of the present application;

[0021] Figure 3 This is a transmission electron micrograph of the co-assembly formed by MBP-SP1-2His and metal chelate ions in Example 2 of the present application;

[0022] Figure 4 This is a transmission electron micrograph of the CdS@Pt@MBP-SP1-2His hybrid in Example 3 of the present application;

[0023] Figure 5 is a transmission electron micrograph of the CdS@MBP-SP1-2His hybrid assembly in Example 4 of the present application;

[0024] Figure 6 This is a comparison of the photocatalytic hydrogen production effects of the samples obtained in Examples 1, 3, and 5 of the present application and Comparative Examples 1-3. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to specific embodiments.

[0027] A method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring comprises the following steps:

[0028] S1. Using genetic engineering methods, MBP was fused to the N-terminus of the sequence within the SP1 ring protein cavity. Based on observation of the protein surface using pyMOL software and combined with computer simulation, suitable sites on the protein surface (amino acids 18 and 98 on the lateral surface) were selected for mutation and introduction of double histidine groups to construct a fusion plasmid. The plasmid DNA was transformed into Escherichia coli BL-21 strain for expression, and the protein mutant solution was purified using anion exchange columns and sephadex columns.

[0029] S2, mixing the protein mutant solution with a CdCl2 solution under nitrogen protection and incubating, and then adding a Na2S solution and incubating again to obtain an SP1 protein-CdS quantum dot hybrid;

[0030] Alternatively, the protein mutant solution is first mixed with an ion chelator (transition metal ions, specifically Fe 2+ 、Co 2+ and Ni 2+ Then, CdCl2 solution was added to the system, and mixed and incubated under nitrogen protection, and finally Na2S solution was added and incubated again to obtain the SP1 protein-CdS quantum dot hybrid assembly.

[0031] The protein used in this application is a cyclic stabilizing protein 1 (SP1), which can spatially confine in situ biosynthesized photocatalyst quantum dots, allowing their size or shape to be controlled, and giving this biological-inorganic hybrid complex excellent photoelectric properties; on the other hand, the two-dimensional layer structure constructed based on protein self-assembly can provide an ideal template skeleton for the artificial photosynthetic catalytic system, achieving its orderly arrangement, thereby increasing its stability and photoelectric separation ability.

[0032] In some embodiments of the present application, in the above-mentioned step S2, the concentration of the protein mutant solution is 0.1-0.5 mM, the concentration of the CdCl2 solution is 0.3-0.5 mM, and the concentration ratio of the Na2S solution to the CdCl2 solution is 1:1.

[0033] In some embodiments of the present application, the concentration ratio of the ion chelator to the protein mutant solution is 0.8-1.8, and the co-incubation time is more than 12 hours.

[0034] In some embodiments of the present application, the mixed incubation time is 0.5-2 hours, and the further incubation time is not less than 5 minutes.

[0035] A semiconductor quantum dot based on protein assembly and peptide anchoring, wherein the semiconductor quantum dot is specifically an SP1 protein-CdS quantum dot hybrid or an SP1 protein-CdS quantum dot hybrid assembly, which is prepared using the above preparation method.

[0036] An application of semiconductor quantum dots based on protein assembly and peptide anchoring in the field of artificial photocatalysis.

[0037] In some embodiments of the present application, the artificial photocatalytic field is photocatalytic hydrogen production. The hydrogen production method is to directly illuminate the semiconductor quantum dots. Conventional values ​​for the intensity and duration of illumination are sufficient, with xenon lamp illumination for 2.5 hours being preferred.

[0038] Furthermore, the above-mentioned photocatalytic hydrogen production step comprises: mixing the SP1 protein-CdS quantum dot hybrid or the SP1 protein-CdS quantum dot hybrid assembly with a noble metal precursor and an electron sacrificial agent, and then irradiating the mixture with light to produce hydrogen. Depositing noble metal nanoparticles on the surface of the semiconductor quantum dots can enhance their photoelectron separation capability.

[0039] In some embodiments of the present application, the above-mentioned precious metal precursor is a high-valent inorganic salt of precious metals such as Pt, Pd, Au, Ru, Mo, and the concentration of the precious metal precursor is 2-20% of the CdS quantum dots; the electron sacrificial agent includes but is not limited to dithiothreitol, triethanolamine or sodium sulfite, and its concentration is 10-80mM.

[0040] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0041] Example 1

[0042] Through genetic engineering, MBP was fused to the N-terminus of the sequence within the SP1 ring protein cavity. The amino acid sites on the protein surface were observed in pyMOL software, which was used to simulate point mutations and observe the residue orientations of the mutated amino acids. Simultaneously, Hex8.0.0 was used for protein molecular docking simulations, ultimately selecting sites 18 and 98 to mutate to histidine. The wild-type SP1 plasmid was genetically engineered to generate the target plasmid. The plasmid DNA was transformed into the Escherichia coli BL-21 strain for expression and purified using anion exchange and dextran gel columns to obtain a protein mutant solution.

[0043] The specific steps of expression are as follows: the plasmid was placed in LB medium containing 100 μg / mL ampicillin (LB medium 10 mL) and cultured at 37°C overnight with shaking. The bacterial liquid was then transferred to 100 mL, 100 μg / mL liquid medium and cultured for 2 hours, and then transferred to 500 mL LB medium containing 100 μg / mL ampicillin and cultured at 37°C with shaking until the OD 600 = 0.6, cooled to 23 ° C and cultured for 30 minutes, then 1mM IPTG was added for induction for 6 hours, and the cells were collected by centrifugation at 8000 rpm for 10 minutes in a low-temperature centrifuge, and the supernatant was discarded. The cells were suspended and washed with physiological sodium chloride solution, and then collected by low-temperature centrifugation under the same conditions. The collected cells were incubated in an ice bath, and the cells were disrupted with a cell crusher. Centrifuged at 15000 rpm for 30 minutes, the supernatant protein solution was retained, and the lower precipitate (organelles and other substances) was discarded to obtain the target protein solution to be purified.

[0044] The specific purification process is as follows: the supernatant protein solution is purified using a DEAE anion column with a 20mM Tris-HCl buffer solution at pH 6.3 as the mobile phase. Elution is performed using a 100-500mM NaCl solution gradient, with the target protein being eluted at both a 350mM gradient and 500mM concentration. The protein is then dialyzed at low temperature, desalted, and concentrated to a dry powder in a freeze dryer. The protein is then re-dissolved in a 20mM PBS solution at pH 7.0, applied to a G75 dextran column to remove nucleic acids, and eluted using the same buffer. The eluted protein solution is dialyzed again and freeze-dried for later use. If the protein powder needs to be stored, it can be sealed and stored at -20°C to prevent deliquescence.

[0045] The above-mentioned protein powder was used to slowly dissolve the protein mutant (MBP-SP1-2His) solution (0.2 mM) by pipetting with ultrapure water. Under nitrogen protection in a glove box, the solution was incubated with CdCl2 (0.3 mM) solution for 1.5 h. Then, a Na2S solution with the same concentration as the CdCl2 solution was added and incubated for 10 min to obtain SP1 protein-CdS quantum dot hybrid (CdS@MBP-SP1-2His).

[0046] Example 2

[0047] A protein mutant (MBP-SP1-2His) solution (0.2 mM) was prepared using the protein dry powder of Example 1, and chelated ions at an equal concentration to the protein mutant were added, and the mixture was incubated at room temperature for 24 h to obtain an MBP-SP1-2His assembly.

[0048] Example 3

[0049] A protein mutant (MBP-SP1-2His) solution (0.2 mM) was prepared using the protein powder of Example 1. The solution was incubated with a CdCl2 (0.4 mM) solution for 2 h under nitrogen protection in a glove box. A Na2S solution of equal concentration to the CdCl2 solution was then added and incubated for more than 5 min to obtain an SP1 protein-CdS quantum dot hybrid (CdS@MBP-SP1-2His).

[0050] A certain concentration of CdS@MBP-SP1-2His was mixed with a noble metal precursor (Pt precursor was used in this example, and the Pt content was 10% of the mass fraction of the formed CdS quantum dots) and an electron sacrificial agent (50 mM), and irradiated with a xenon lamp to obtain a CdS@Pt@MBP-SP1-2His hybrid.

[0051] Example 4

[0052] A protein mutant (MBP-SP1-2His) solution (0.2 mM) was prepared using the protein powder of Example 1. An equal concentration of chelated ions was added and the mixture was incubated at 4°C for more than 12 h to obtain an MBP-SP1-2His assembly. The assembly solution was incubated with a CdCl2 (0.4 mM) solution for 0.5 h under nitrogen protection in a glove box. A Na2S solution of equal concentration to the CdCl2 solution was then added and incubated for 20 min to obtain an SP1 protein-CdS quantum dot hybrid assembly (CdS@MBP-SP1-2His Assembly).

[0053] Example 5

[0054] A 0.2 mM protein mutant (MBP-SP1-2His) solution was prepared using the dry protein powder from Example 1. A chelating ion (at a 1.5:1 protein concentration ratio) was added and incubated at room temperature for 24 h to obtain an MBP-SP1-2His assembly. This assembly solution was incubated with a 0.5 mM CdCl2 solution for 0.5 h under nitrogen in a glove box. A Na2S solution of equal concentration to the CdCl2 solution was then added and incubated for 20 min. The solution was then mixed with a noble metal precursor (in this example, a Pt precursor was used, with a Pt content of 10% of the mass fraction of the formed CdS quantum dots) and an electron sacrificial agent (20 mM). The mixture was then irradiated with a xenon lamp to obtain a CdS@Pt@MBP-SP1-2His hybrid assembly.

[0055] Comparative Example 1

[0056] Under nitrogen protection in a glove box, a Na2S solution with the same concentration as that of the CdCl2 solution was added to the CdCl2 (0.3 mM) solution and incubated for 10 min to obtain CdS directly prepared in the solution.

[0057] Comparative Example 2

[0058] Under nitrogen in a glove box, a Na2S solution of equal concentration was added to a CdCl2 (0.3 mM) solution and incubated for 10 minutes to obtain CdS directly in solution. This solution was then mixed with a noble metal precursor (in this example, a Pt precursor was used, with a Pt content of 10% of the mass fraction of the resulting CdS quantum dots) and an electron sacrificial agent (20 mM). The mixture was then irradiated with a xenon lamp to produce CdS@Pt.

[0059] Comparative Example 3

[0060] A protein mutant (MBP-SP1-2His) solution (0.2 mM) was prepared using the protein dry powder of Example 1. Under nitrogen protection in a glove box, the solution was mixed with a noble metal precursor (a Pt precursor was used in this example, with a Pt content of 10% of the mass fraction of the formed CdS quantum dots) and an electron sacrificial agent (20 mM). The mixture was then irradiated with a xenon lamp to obtain Pt@MBP-SP1-2His.

[0061] Comparative Example 4

[0062] A protein mutant (SP1-2His) solution (0.2 mM) without fusion of anchor peptide was prepared and incubated with CdCl2 (0.3 mM) solution for 1.5 h under nitrogen protection in a glove box. Then, a Na2S solution with the same concentration as the CdCl2 solution was added and incubated for 10 min to obtain a non-anchored SP1 protein-CdS quantum dot hybrid (CdS@SP1-2His).

[0063] Experimental example

[0064] 1. Scanning electron microscopy characterization

[0065] The samples prepared in Comparative Example 1 and Examples 1-4 were characterized by transmission electron microscopy. Figure 1-5 Compare Figure 1-5 It can be seen that the photocatalyst prepared by the method described in this application has obvious lattice stripes and quantum dot structures. Specifically: Compared with Comparative Example 1 ( Figure 1 ) solution directly formed CdS, compared with Example 1 ( Figure 2 ) and Example 3 ( Figure 4 ) of CdS@MBP-SP1-2His and CdS@Pt@MBP-SP1-2His protein-inorganic nanoparticle hybrids both have their characteristic lattice fringes, indicating that they are monodisperse and not aggregated. Example 4 ( Figure 5 ) in which the nanoparticles are orderly arranged on the surface of the protein template.

[0066] 2. Photocatalytic hydrogen production experiment

[0067] The specific method is as follows:

[0068] Under nitrogen protection in a glove box, a photocatalytic sample solution was prepared in a sample bottle and sealed before measurement. The samples in Examples 1, 3, and 5 and the samples in Comparative Examples 1-3 were prepared into 400 μL of the sample to be tested. After the sample bottle was completely sealed, it was taken out of the glove box and a solar light hydrogen production experiment (xenon lamp, 150 mW·cm -2 The sample was placed in a 4°C constant temperature bath for protection). The total amount of hydrogen produced by the sample was determined by gas chromatography.

[0069] Gas chromatography analysis was performed on an Agilent 8890 gas chromatograph system, with each measurement performed in triplicate at 25°C. The molar concentration of photogenerated H₂ gas in each sample was analyzed using a gas chromatograph (G3540-60000, Agilent, 8890 GC). (Sampling method: gas-tight needle injection; carrier gas: air; inlet volume: 1 mL; headspace: 1.6 mL).

[0070] The photocatalytic hydrogen production performance of the samples in Examples 1, 3, and 5 and Comparative Examples 1-3 is as follows: Figure 6 As shown, the hydrogen production rate of Example 5 shows a significant advantage, per mg of Cd 2+ The corresponding hydrogen production rate can reach 69.1 μmol / h, which is 80.1 times that of Comparative Example 1 and 18.9 times that of Comparative Example 2, where Pt is directly deposited on the surface. In contrast, Example 3 can reach 52.1 μmol / h, approximately 14 times that of Comparative Example 2. The hydrogen production performance of Comparative Example 3 indicates that the improved catalytic efficiency of the system stems from the protein-inorganic nanoparticle hybrids confined within the protein cavity.

[0071] In summary, the semiconductor quantum dots based on protein assembly and peptide anchoring, their preparation method, and their application in the field of artificial photocatalysis according to the embodiments of the present application have the following advantages:

[0072] This application describes the in situ biosynthesis of semiconductor quantum dots based on proteome assembly and peptide anchoring. The protein template is highly designable, allows for directional modification, and exhibits high biocompatibility. The building block is the cyclic stabilizing protein 1 (SP1), which incorporates a metal-binding peptide within its natural 4nm cavity, enabling spatially confined anchoring and in situ growth of CdS quantum dot photosensitizers.

[0073] 2. The semiconductor quantum dots prepared in this application are based on protein assembly, which can orderly arrange the catalytic center quantum dots synthesized in situ, enhance their photoelectric separation performance, effectively avoid the random aggregation of inorganic nanoparticles, and thus improve the stability of the catalytic system.

[0074] 3. Experiments have shown that depositing noble metal nanoparticles on the surface of semiconductor quantum dots to form a heterojunction structure can effectively improve the performance of photocatalytic hydrogen production.

[0075] In summary, the semiconductor quantum dots based on protein assembly and peptide anchoring in this application are highly designable and modifiable, can be adapted to a variety of electron sacrificial agents to achieve efficient hydrogen production, are highly stable and can arrange photosensitizers and photocatalytic centers in an orderly and targeted manner, showing great development prospects and application potential.

[0076] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

Claims

1. A method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring, characterized in that: The following steps are involved: S1. Using genetic engineering methods, MBP was fused to the N-terminus of the sequence within the SP1 ring protein cavity, and a double histidine group was introduced by mutation at a suitable site on the protein surface to construct a fusion plasmid. The plasmid DNA was transformed into the Escherichia coli BL-21 strain for expression, and purified using anion exchange columns and dextran gel columns to obtain a protein mutant solution. S2, mixing the protein mutant solution with a CdCl2 solution under nitrogen protection and incubating, and then adding a Na2S solution and incubating again to obtain an SP1 protein-CdS quantum dot hybrid; Alternatively, the protein mutant solution is first incubated with an ion chelator, and then a CdCl2 solution is added to the system, mixed and incubated under nitrogen protection, and finally a Na2S solution is added and incubated again to obtain an SP1 protein-CdS quantum dot hybrid assembly.

2. The method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring according to claim 1, characterized in that: In the S2 step, the concentration of the protein mutant solution is 0.1-0.5 mM, the concentration of the CdCl2 solution is 0.3-0.5 mM, and the concentration ratio of the Na2S solution to the CdCl2 solution is 1:

1.

3. The method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring according to claim 2, characterized in that: The concentration ratio of the ion chelator to the protein mutant solution is 0.8-1.8, and the co-incubation time is more than 12 hours.

4. The method for preparing semiconductor quantum dots based on protein assembly and peptide anchoring according to claim 1, characterized in that: The mixed incubation time is 0.5-2 hours, and the further incubation time is not less than 5 minutes.

5. A semiconductor quantum dot based on protein assembly and peptide anchoring, characterized in that: The semiconductor quantum dots are specifically SP1 protein-CdS quantum dot hybrids or SP1 protein-CdS quantum dot hybrid assemblies, which are prepared by the preparation method according to any one of claims 1 to 4.

6. Application of the protein-assembled and peptide-anchored semiconductor quantum dots according to claim 5 in the field of artificial photocatalysis.

7. The use of semiconductor quantum dots based on protein assembly and peptide anchoring in the field of artificial photocatalysis according to claim 6, characterized in that: The field of artificial photocatalysis is photocatalytic production of hydrogen.

8. The use of semiconductor quantum dots based on protein assembly and peptide anchoring in the field of artificial photocatalysis according to claim 7, characterized in that: The photocatalytic hydrogen production step comprises: mixing an SP1 protein-CdS quantum dot hybrid or an SP1 protein-CdS quantum dot hybrid assembly with a noble metal precursor and an electron sacrificial agent, and then producing hydrogen by light stimulation.

9. The use of semiconductor quantum dots based on protein assembly and peptide anchoring in the field of artificial photocatalysis according to claim 8, characterized in that: The noble metal precursor is a high-valent inorganic salt of noble metal, and the concentration of the noble metal precursor is 2-20% of the CdS quantum dots; the electron sacrificial agent includes dithiothreitol, triethanolamine or sodium sulfite, and the concentration thereof is 10-80 mM.

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